System and method for processing a preform vacuum vessel to produce a structural assembly

Abstract

A system and method for processing a preform in a vacuum vessel to produce a structural assembly are provided. The system includes a heated die set defining a cavity in which the preform can be formed, bonded, or otherwise processed. The die set is disposed in a cavity of the vacuum vessel from which gas can be evacuated. Thus, a pressurized fluid can be provided to the preform, e.g., to an interior space of the preform to form or constrain the preform in the die cavity, and the vacuum vessel can be evacuated so that the die set, and typically the preform, are exposed to a pressure that is reduced relative to the ambient pressure. Further, the vacuum vessel can constrain the die set in the closed position during processing.

What is claimed is: 
     
       1. A sheet forming system comprising:
 a die set including dies configured to cooperably define a die cavity configured to receive a preform, the die cavity including a contour surface corresponding to a desired contour of the structural assembly; 
 a heater configured to heat the preform in the die cavity; 
 a fluid source configured to provide a pressurized fluid to the die cavity to form the preform against the contour surface; 
 a vacuum vessel having portions configured to cooperably define a substantially scaled vessel cavity adapted for receiving the die set, the sealed vessel cavity corresponding in size to the die set such that the vacuum vessel is configured to retain the die set in a closed position; and 
 a vacuum device in fluid communication with the vessel cavity of the vacuum vessel, the vacuum device being configured to evacuate gas from the vacuum vessel and reduce the pressure in the vacuum vessel to less than the ambient pressure. 
 
     
     
       2. A system according to  claim 1  wherein the heater is disposed at least partially in at least one die. 
     
     
       3. A system according to  claim 1  wherein the heater includes an electrically resistive element disposed in at least one die. 
     
     
       4. A system according to  claim 1 , further comprising at least one fluid connector extending from an outer surface of the vacuum vessel to the vessel cavity and defining a fitting in the vessel cavity configured to be connected to the preform such that the fluid connector is configured to fluidly connect the fluid source to the die cavity. 
     
     
       5. A system according to  claim 1 , further comprising at least one electrical connector extending from an outer surface of the vacuum vessel to the vessel cavity. 
     
     
       6. A system according to  claim 1 , further comprising a temperature gauge configured to detect a temperature of the preform. 
     
     
       7. A system according to  claim 1 , further comprising a controller configured to control the operation of the fluid source according to the temperature of the preform and the pressure in the vacuum vessel. 
     
     
       8. A system according to  claim 1  wherein the dies are adjustable relative to the vacuum vessel such that the vacuum vessel is configured to be partially opened while the die set is closed. 
     
     
       9. A system according to  claim 1 , further comprising an electrical power source configured to selectively power the heater according to a pressure in the vacuum vessel. 
     
     
       10. A system according to  claim 1 , further comprising at least one fluid seal for sealing the vessel cavity. 
     
     
       11. A sheet forming method comprising the steps of:
 disposing at least one sheet in a die cavity defined by a die set; 
 disposing the die cavity in a vacuum cavity of a vacuum vessel; 
 heating the sheet in the die cavity; 
 evacuating gas from the vacuum cavity to reduce the pressure in the vacuum cavity to a pressure less than the ambient pressure, such that the vacuum cavity corresponds in size to the die set and the vacuum vessel retains the die set in a closed position; and 
 forming the sheet by introducing a pressurized fluid to the die cavity to press the sheet against a contour surface of the die set. 
 
     
     
       12. A method according to  claim 11  further comprising injecting an inert gas to an interior of a preform defined by the sheet via at least one gas connection extending from the vessel cavity and evacuating the inert gas from the preform. 
     
     
       13. A method according to  claim 11  wherein said heating step comprises electrically energizing heater elements disposed in the dies. 
     
     
       14. A method according to  claim 11 , further comprising measuring the temperature of the sheet. 
     
     
       15. A method according to  claim 11  wherein said injection of the pressurized fluid is controlled according to the temperature of the sheet and the pressure in the vacuum vessel. 
     
     
       16. A method according to  claim 1  wherein the die set has at least two dies, each die being adjustable relative to the vacuum vessel such that the vacuum vessel is configured to open partially while the die set remains closed. 
     
     
       17. A method according to  claim 11  wherein said heating step comprises heating the sheet according to the pressure in the vacuum vessel to thereby prevent heating of the sheet when the vacuum vessel is pressured in at least one range of pressure. 
     
     
       18. A sheet forming system comprising:
 a die set including dies configured to cooperably define a die cavity configured to receive a preform, the die cavity including a contour surface corresponding to a desired contour of the structural assembly; 
 a heater configured to heat the preform in the die cavity; 
 a fluid source configured to provide a pressurized fluid to the die cavity to form the preform against the contour surface; 
 a vacuum vessel having portions configured to cooperably define a substantially sealed vessel cavity adapted for receiving the die set, the sealed vessel cavity corresponding in size to the die set such that the vacuum vessel is configured to retain the die set in a closed position; and 
 a vacuum device in fluid communication with the vessel cavity of the vacuum vessel, the vacuum device being configured to evacuate gas from the vacuum vessel and reduce the pressure in the vacuum vessel to less than the ambient pressure, 
 wherein the dies are adjustably connected to the vacuum vessel such that the dies are configured to be opened by opening the vacuum vessel and the vacuum vessel is configured to be partially opened while the die set is closed. 
 
     
     
       19. A sheet forming method comprising the steps of:
 disposing at least one sheet in a die cavity defined by a die set; 
 disposing the die cavity in a vacuum cavity of a vacuum vessel; 
 heating the sheet in the die cavity; 
 evacuating gas from the vacuum cavity to reduce the pressure in vacuum cavity to a pressure less than the ambient pressure; and 
 forming the sheet by introducing a pressurized fluid to the die cavity to press the sheet against a contour surface of the die set, 
 wherein the die set has at least two dies, each die being adjustably connected to the vacuum vessel such that the dies are configured to be opened by opening the vacuum vessel and the vacuum vessel is configured to open partially while the die set remains closed.